Awesome build! I want to build one too but I have a slightly different idea.
I want to start with an old galvanized 2 wheel boat trailer. Preferably an 18 footer or more. I think I'll have to fill the tires with liquid to keep the weight out on the end, but also to keep it from digging too deep. I want to put a hinged 3 point system on the back end of the trailer, using hydraulics to swivel it down into "dig" position. I figured I'd just use the drawbar on the tractor with a trailer ball to operate it. I would weld a long piece of square stock, cut into sections and welded into a "C" (for ground clearance as needed) to the front of the trailer to extend it further into the pond. I don't have cattails, but plenty of other shoreline vegetation. I was also thinking of using it with my 6' box blade to pull out silt. This would be a slow process, needing to let the dredged silt dry for a week or more in order to scoop it up with the FEL and haul it to low areas needing fill.
It would be nice to have a skid steer to operate it with so not so much neck craning. I haven't thought about hooking in place of the FEL bucket and using that to raise and lower the angle of attack. Hummmm.